1. Field of the Invention
This invention relates generally to bearings and, more particularly, to roller bearings that include a cage structure with slots for receiving the bearing rollers.
2. Description of the Related Art
Roller bearings reduce friction between two bodies, one or both of which are rotating. Roller bearings include an outer ring and an inner ring that define an annular space in which a group of rollers can roll, orbiting about the bearing axis. The outer ring is attached to one of the bodies, and the inner ring is attached to the other body. The roller bearing reduces friction resulting from relative rotational movement between the inner ring and outer ring. The friction is reduced by rotation of the rollers in the annular space on ring surfaces known as races. The bearing transmits bearing axial and radial loads from one ring to the other through the rollers. Often, roller bearings use tapered rollers that have a conical cylindrical shape, with one end face having a larger diameter than the other. When a radial load is applied to a conical roller, the conical shape causes the roller to experience an axial load.
In a conventional roller bearing, the rollers are kept in the annular space between the races by shoulders protruding from the circumferences of one of the rings. The roller axial loads are transmitted along the longitudinal axes of the rollers, and out the large diameter roller end faces to one of the shoulders protruding from the circumference of the other ring. This is known as end loading of the rollers. A conventional bearing can also include a slotted cage structure that keeps the rollers separated from each other, so they do not collide as they roll, and that orbits with the rollers.
There necessarily is sliding contact between the shoulder of the race and the large diameter end face of each roller as the roller rolls along the race, because the roller end face -abuts the shoulder as the roller rotates. The sliding contact creates friction, which produces heat and reduces the survivability of the bearing. It is important to control friction, because it can quickly generate enough heat to disintegrate a bearing. If a bearing doesn't have enough lubrication to control the friction, the friction can produce enough heat to destroy the bearing, and there will be an abrupt halt to rotation.
It is sometimes necessary to react bearing loads in more than one axial direction, and in this circumstance either a crossed roller bearing or multiple rows of alternately-inclined bearings are necessary. The great advantage of crossed roller bearings is that they only require the space of a single-row bearing. Crossed roller bearings include alternatingly-inclined rollers in a single row, and allow the crossed roller bearing to handle axial loads in the manner of a multiple single-row bearing. That is, a crossed bearing with a single row of alternatingly inclined rollers performs the work of multiple single-row bearings. A detrimental aspect of a crossed roller bearing is that the end faces of one set of alternating rollers are in sliding contact with the race used by the oppositely inclined set of rollers, and therefore the races are subjected to both rolling and sliding forces, and can become scarred and pitted. Crossed roller bearings also generally have a greater amount of friction to contend with, and are not suitable for speeds as high as those of conventional roller bearings.
Thus, in the case of either a conventional tapered roller bearing or a conventional crossed roller bearing, friction is generated at the point of contact between the roller end face and the load-bearing ring surface (either the ring shoulder or the race, respectively). The friction decreases the maximum bearing speed, reduces the survivability of the bearing, increases the lubrication requirements, and limits the applications for which the bearing is suitable.
From the foregoing discussion, it should be apparent that there is a need for a roller bearing that provides a reduced amount of friction while reacting conical roller axial loads. The present invention satisfies this need.